The present invention relates particularly to transceiver circuitry, a portable communication device and to a method for performing radio communication.
Digital portable communication devices for communicating voice signals have been successfully developed and manufactured. In particular, GSM devices have been particularly successful for communicating voice signals. However, voice signals require only a relatively small bandwidth compared to video or other multimedia signals. In order to provide communication devices with a larger bandwidth capability for transmitting data signals such as video signals, it has been proposed to develop a device which incorporates a data portion for dealing with data signals requiring a higher bandwidth than voice signals. The data portion achieves the higher bandwidth by using a higher order of modulation compared to GSM. The use of a higher order of modulation will require new base stations to be deployed which are capable of dealing with the higher order of modulation, and each such base station will only be able to cover a smaller geographical area than a conventional GSM base station. For these reasons, the data portion will often not be able to work in places where a conventional GSM communication device would be able to work unless and until full coverage by the new base-stations is achieved. Therefore, according to one proposal for providing an improved data rate, referred to as Enhanced Data-rate for GSM Evolution (EDGE) it is proposed that all larger data capability devices will also include a separate GSM portion for dealing with voice signals.
According to a first aspect of the present invention, there is provided transceiver circuitry comprising: a first portion, having a first modulation means operating at a first order of modulation, for transmitting and receiving voice signals; a second portion, having a second modulation means operating at a second order of modulation, for transmitting and receiving digital signals at a higher data rate than is achievable by the first portion; and a data conversion means operable to convert from or into voice signals intended for processing by the first portion into or from digital signals for processing by the second portion.
The term order of modulation is used here to refer to the number of bits which each transmitted or received symbol represents. Thus in GSM, a modulation scheme referred to as GMSK (Gaussian Minimum Shift Keying) is used in which each symbol represents only a single bit, and this corresponds to a single order of modulation. In an alternative modulation scheme referred to as 8PSK, each symbol represents 3 bits of data which corresponds to a triple order of modulation. According to a preferred embodiment of the present invention, the first order of modulation is preferably a single order of modulation, and the second order of modulation is preferably a triple order of modulation although it may be only a double order of modulation.
Transceiver circuitry according to the present invention enables certain advantages associated with sending voice signals at a higher data rate than is achievable by the GSM portion. For example, when a higher data rate is available for sending voice signals (because a base station and handset both able to demodulate the higher order of modulation are sufficiently close to one another), it is possible to provide more protection to the encoded voice signals to render the signals less susceptible to distortion as a result of interference on the channel, etc. Alternatively, in a particularly advantageous embodiment, it is possible to use voice signals encoded by a vocoder adapted for use with GMSK modulation in a full rate type multiplexing scheme in which one time-slot is required in every Time Division Multiple Access (TDMA) frame (i.e. a full-rate vocoder), in a half-rate type multiplexing scheme which requires an allocation of only one time-slot in every two TDMA frames with 8PSK modulation, thus permitting twice as many users in a single cell as in the conventional case (i.e. Twice as many as would be possible with a GSM device using a full-rate vocoder) without the disadvantages associated with using a half-rate vocoder (ie of using less information to represent the speech signal input to the vocoder and thus being more susceptible to errors associated with of the loss of one or more bursts).
The basic multiplexing schemes (FR and HR) used in higher order of modulation are the same as in lower order of modulation. The same mapping of bursts in the TDMA frames apply.
Furthermore, the data conversion means according to the present invention may be surprisingly simple as result of the use by the second portion of a higher order of modulation resulting in an integer-multiple increase in the data rate available via the second portion compared with the first (GSM) portion (e.g. 2 or 3, etc. times the data rate achievable by the first portion). Additionally, conventional GSM vocoders may be used in the device according to the present invention and they may be used to generate or to decode the signals to be transmitted or having been received by either the first or second portions. That is to say, that the data conversion means will simply work with the conventional GSM vocoders and does not require any vocoding means of its own.
The data conversion means preferably comprises a digital signal processor with some spare processing capacity. According to one preferred embodiment, the data conversion means comprises a channel coding means together with a multiplexing and interleaving means and a controller able to alter the mode of operation of the channel coding means and the multiplexing and interleaving means in such a way as either to provide bursts of data suitable for modulation by the first modulation means or by the second modulation means.
According to a second aspect of the present invention, there is provided a communication device comprising transceiver circuitry comprising: a first portion, having a first modulation means operating at a first order of modulation, for transmitting and receiving voice signals; a second portion, having a second modulation means operating at a second order of modulation, for transmitting and receiving digital signals at a higher data rate than is achievable by the first portion; and a data conversion means operable to convert from or into voice signals intended for processing by the first portion into or from digital signals for processing by the second portion.
According to a third aspect of the present invention, there is provided a method of transmitting a voice signal comprising the steps of generating a first data signal representative of the voice signal to be transmitted, selecting between a first portion, having a first modulation means operating at a first order of modulation, for transmitting and receiving voice signals, and a second portion, having a second modulation means operating at a second order of modulation, for transmitting and receiving digital signals at a higher data rate than is achievable by the first portion, and, if the second portion is selected, converting the first data signal representative of the voice signal to be transmitted into a second data signal representative of the voice signal to be transmitted.
Preferably the step of selecting between the first and second portions includes assessing whether or not the second portion is in a location where it is able to communicate with a suitable receiver. That is to say, if a receiver capable of demodulating the signals transmitted by the second portion is sufficiently close to the device containing the second portion as to be able to receive signals transmitted by the second portion without excessive distortion, then the second portion will preferably be selected; otherwise, the first portion will preferably be selected.
According to a fourth aspect of the present invention, there is provided a method of receiving a voice signal comprising the steps of selecting between a first portion, having a first modulation means operating at a first order of modulation, for transmitting and receiving voice signals, and a second portion, having a second modulation means operating at a second order of modulation, for transmitting and receiving digital signals at a higher data rate than is achievable by the first portion, and, if the second portion is selected, converting the output signal from the second portion into a digital voice signal for conversion by a suitable GSM decoder.
Preferably the step of selecting between the first and second portions includes assessing whether or not the second portion is in a location where it is able to communicate with a suitable transmitter. That is to say, if a transmitter capable of modulating the signals for reception by the second portion is sufficiently close to the device containing the second portion as to be able to transmit signals to the second portion without excessive distortion, then the second portion will preferably be selected; otherwise, the first portion will preferably be selected.